The invention relates generally to a multiplexing scheme in a network that joins a number of nodes. More particularly, but not exclusively, the invention relates to a multiplexing scheme in a System Area Network for connecting processor nodes and I/O nodes.
One example of a System Area Network (SAN) is that proposed by the Infiniband™ (IB) Trade Association. The IB SAN is used for connecting multiple, independent processor platforms (i.e., host processor nodes), input/output (I/O) platforms, and I/O devices. The IB SAN supports both I/O and interprocessor communications for one or more computer systems. An IB system can range from a small server with one processor and a few I/O devices, to a parallel installation with hundreds of processors and thousands of I/O devices. Furthermore, the IB SAN allows bridging to an internet, intranet, or connection to remote computer systems. IB provides a switched communications fabric allowing many devices to concurrently communicate with high bandwidth and low latency. An end node can communicate over multiple IB ports and can utilize multiple paths through the IB fabric. The multiplicity of IBA ports and paths through the network are exploited for both fault tolerance and increased data transfer bandwidth. IB hardware off-loads from the central processing unit much of overhead associated with the I/O communications operation. In an IB SAN, the data itself is carried between nodes on 1, 4 or 12 physical links.
Another example of a SAN is the Servernet™ processor and I/O interconnect by Compaq Computer Corporation.